Curable coating compositions such as thermoset coatings are widely used in the coatings art. They are often used for topcoats in the automotive and industrial coatings industry.
High-gloss and color-plus-clear composite coatings are particularly useful as topcoats where exceptional gloss, depth of color, distinctness of image, or special metallic effects are desired. The automotive industry has made extensive use of these coatings for automotive body panels. These coatings require an extremely high degree of clarity and a low degree of visual aberrations at the surface of the coating in order to achieve desired visual effects such as a high distinctness of image (DOI).
As a result, high-gloss and composite color-plus-clear coatings are susceptible to a phenomenon known as environmental etch. Environmental etch manifests itself as spots or marks on or in the finish of the coating that often cannot be rubbed out. It is often difficult to predict the degree of resistance to environmental etch that a high gloss or color-plus-clear composite coating will exhibit. Many coating compositions known for their durability and/or weatherability when used in exterior paints, such as high-solids enamels, do not provide the desired level of resistance to environmental etch when used in high gloss coatings and colorplus-clear composite coatings.
Many compositions have been proposed for use as the clearcoat of a color-plusclear composite coating, such as polyurethanes, acid-epoxy systems and the like. However, many prior art systems suffer from disadvantages such as coatability problems, compatibility problems with the pigmented basecoat, solubility problems. Moreover, very few one-pack coating compositions have been found that provide satisfactory resistance to environmental etch, especially in the demanding environment of automotive coatings.
It has been found that carbamate functional polymers such as those described in U.S. Pat. No. 5,356,669 can be used to provide coating compositions which exhibit significantly improved environmental etch resistance. Carbamate functional polymers have been used to provide commercially advantageous coatings compositions, especially as clearcoats in composite color-plus-clear coatings.
Unfortunately, some carbamate functional compounds and/or polymers known in the prior art are vulnerable to instability and decomposition, especially with respect to the formation of cyclic carbonates and carbamates. This results in difficulties in manufacturing and storage.
Moreover, it has heretofore been difficult to make hydroxy functional mono-carbamate functional compounds in an efficient and cost effective manner. In particular, what is desired is a commercially feasible method of making such compounds that utilizes cost effective starting compounds such as polyols and diols.
The prior art has failed to address and rectify these issues.
The preparation of monocarbamate alcohols by the ammonolysis of cyclic carbonates prepared from substituted propanediols is disclosed in Some Anticonvulsant Agents Derived from 1,3-Propanediols, Ludwig, B. J. and Piech, E. C.; J. Am Chem. Soc. (1951) 73 5779-81. CAN 47:3228.
U.S. Pat. No. 5,719,237, Rehfuss et al., discloses the use of carbamate functional compounds (a) having a plurality of carbamate groups prepared by a transcarbamylation reaction wherein an alcohol or hydroxylalkyl carbamate is reacted with an alkyl carbamate. The '237 patent teaches that it is desirable to avoid the inclusion of hydroxyl groups in compound (a) as such hydroxyl groups lead to the formation of vulnerable ether bridges.
U.S. Pat. No. 5,907,024, Ohrbom et al., and U.S. Pat. No. 5,945,499 disclose the use of hydroxyalkyl carbamates of the general structure—C(OH)—(CH2)n—O—C(O)—NHRwherein n is an integer from 0 to 6 and R is H or an alkyl group of from 1 to 4 carbons.
U.S. Pat. No. 5,760,127, Bammel et al, and U.S. Pat. No. 6,262,297, Clements et al., disclose hydroxyalkylcarbamate compositions produced by the reaction of anhydrous ammonia or aqueous ammonium hydroxide with a six-membered cyclic carbonate. Bammel et al discloses that five-membered rings are preferred, not as a result of better performance, but as a result of their ease of synthesis and greater degree of commercial availability. Clements et al teaches that six-membered rings are preferred due to increased stability. However, the cost and commercial availability of the six-membered cyclic carbonates renders the process and resultant products to be less than cost effective. Also, depending on the location of any substituent groups on the starting cyclic carbonate, the process disclosed in Clements produces a reaction product which is a compound comprising a mixture of structures with varying reactivity and selectivity.
WO 0156978, Rink, et al discloses positionally isomeric diethyloctanediol dicarbamates and diethyloctanediols diallophanates. The dicarbamate and diallophanate species have no hydroxyl functionality and are made from position isomers of diethyloctane diols.
Despite these and other attempts by the prior art, the prior art has failed to provide a cost effective and efficient manner of making hydroxy functional mono-carbamate functional compounds from polyols and diols. Moreover, the prior art has particularly failed to provide such hydroxy functional mono-carbamate functional compounds that possess improved stability with respect to decomposition and the formation of undesirable cyclic carbonates and carbamates.
Accordingly, it is an object of the invention to provide a reactive compound suitable for use in coating compositions as an additive or reactive diluent or as a reactant to make reactive polymers and/or oligomers. Such a reactive compound should simultaneously provide improvements in reactivity, stability, and reaction selectivity.
In particular, it is an object of the invention to provide reactive compounds having primary carbamate functionality and either halide or hydroxy functionality and that possess improved stability with respect to the decomposition and the formation of undesirable cyclic carbonates and carbamates.
It is a further object of the invention to provide a cost effective and efficient method of making such reactive compounds.
It is a further object of the invention to provide a cost effective and efficient method of using particular polyols and diols to make the desired reactive compounds.